DNA replication

1. DNA helicase unzips DNA

hydrogen bonds between complementary base pairs break, and 2 strands separate

2. nucleotides bind to exposed strands

free DNA nucleotides bind to their complementary bases on the exposed DNA starnds

3. DNA polymerase forms phosphodiester bonds

forms phosphodiester bonds between adjacent free nucleotides to bind the new strand to the old strand (by condensation reactions)

DNA replication

produces 2 identical DNA molecules, with each new molecule containing one strand from the original DNA molecule and one newly synthesised strand

leading strand

the template strand in which DNA polymerase can move continually in the same direction (3’ to 5’)

lagging strand

the template strand in which DNA polymerase cannot continually move, instead the DNA polymerase builds in fragments (3’ to 5’)

mutations

a change in the sequence of nucleotides, occur randomly and can be harmful as a different protein / non functional protein may be made

importance of replication

when cells divide, the DNA from the original parent cell is copied by semi-conservative replication to ensure that the genetic code is copied so proteins can be synthesised